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Questions tagged [optics]

Optics is the study of light, and its interaction with matter. It includes topics such as imaging systems, fiber optics, lasers, quantum optics, and more.

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Why does frequency remain unchanged in light refraction but wavelength doesn't?

Since the frequency of an electromagnetic wave does not change during refraction but the velocity changes, the wavelength must therefore change. But why doesn't the frequency change in the first place?...
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Lens simulator with geometrical optics [duplicate]

I'm looking for a lens simulator to see rays from geometrical optics, possibly easy to use. For now I'm playing with OpticalRayTracer that works perfectly for a preliminary simulation. I would like a ...
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Laser beam diameter with Interferometer

Is it possible to measure laser beam diameter used as a source in an interferometer? If so, then how to go about designing such an interferometer?
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23 views

Beamsplitter complex notation

I am trying to understand the formalism presented in this paper about the transmission of a fiber ring resonator. By modelling the coupler as a beamsplitter, the authors write: $$E_{2}=rE_{1}+itE_{3}$...
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Temporal period to frequency conversion (optical cavity)

Why is it that the Finesse and resonance width of a cavity calculated in time domain is different from that calculated in frequency domain? Here is a temporal signal that I recorded with a photodiode ...
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60 views

2 windows - will I see the reflections?

I have a question regarding photons nature. Let's say I have a single source of light - regular bulb and the observer - in the same room. The observer looks through a glass window (normal glass ...
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How does reflection and refraction of light behave for a colloidal solution of glass nanoparticles?

If I have a colloidal solution of glass nanoparticles (10-100nm diameter), how much of an effect does refraction and total internal reflection have on the transmission of the light? I know that if the ...
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1answer
46 views

How do photons encode images?

When light bounces off an object, the light then travels into the eye of an observer who can then reconstruct the image. Do the photons encode the image and how do they do so?
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Drude AC-permittivity and relation to interband/intraband transition

The the relative permittivity of a metal in an ac-electric field is usually described by the drude-model (SI-units) $$ \epsilon=1-\frac{n_e e^2}{m^* \epsilon_0 \omega^2} \frac{1}{1+i\nu/\omega} $$ See ...
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Do the results of this laser experiment demonstrate nonlinear optical phenomenon?

In my photonics class, we conducted an experiment to observe the Beer-Lambert law and the effects of filters(absorption, transmittance, and reflection). We shined a red(632nm) 5mW Helium-Neon laser ...
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1answer
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Can I (in principle) make an analog fibrescope/borescope for consumer phones using only a fibre optic cable?

This question is testing my (limited) understanding of optics. Here is the background. Many endoscopes work by using a fiber optic light guide to transmit light to a camera which sits at the end of ...
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Doppler Shift in Michelson-Interferometer

I've used a michelson interferometer with a moveable mirror in order to verify the doppler effect for light waves. But whilst writing the theory for my lab report I encounterd an issue I'm not able to ...
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Double-slit diffraction: is $x$ measured from the centre to the fringe, or between the fringes on either side?

In using the formula $\lambda = \frac{ax}{D}$, is $x$ (the fringe separation) measured from the centre to the fringe, or between the fringes on either side of the centre? In other words, in the ...
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Is it possible to manipulate the polarization of unpolarized light within a medium via Electric field?

You see this setup above. There is an unpolarized light source travelling through a transparent dielectric medium. Think of this triangular shaped medium as a capacitor. there are 3 conductive sides ...
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1answer
53 views

Would 2 people wearing identical night vision goggles be able to see each other from afar? [on hold]

From what I understand, this is how night vision goggles (NVGs) function: The environment is illuminated by forward facing IR LEDs. A portion of the light bouncing off of the scene passes through an ...
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Does light take the path of least time because it travels in straight lines or vice versa?

My question is which of these two feats is a consequence of the other? Light travels in straight lines, mostly. Does it do that as a result of Fermat's principle of least time? and if so, is there a ...
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Rotating Frame Transformation for three level system

I am trying to solve a task from an exercise sheet: We consider a three-level system ($\Lambda$-configuration) with three eigenstates $|1\rangle$, $|2\rangle$ and $|3\rangle$. The levels $|1\rangle$ ...
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Image of an Isosceles triangle kept on the focus of a u concave mirror

Consider the question and the diagram in the following link. Question What will be it's image? I got it for 2 points on the horizontal line, one will be at infinity. For the slant line, do we ...
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Does electric field vector of a extraordinary ray always vibrates along the direction of the optic axis? If yes, then why?

Wherever I study about Extraordinary ray, it is assumed everywhere that its direction of vibration of the electric field is always along the optical axis. Is it all the way? Is this a general property ...
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14 views

For the high-frequency permittivity of a material, do I need to look beyond its value in the optical energies region?

I was trying to find $\varepsilon_\infty$ for InSb, and the value I found on Kittel p. 416 was 15.6. But in the literature, even at 6 eV, $\varepsilon (\omega )$ is still in the negative (at -3.835) ...
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1answer
34 views

Optics for photographing degree of polarization?

It's relatively common practice in photography to use a polarizing filter to get rid of reflections from non-metallic surfaces. Usually you just put this filter in front of the lens and rotate it ...
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1answer
22 views

How to estimate a complex (imaginary) refractive index from absorbance?

In order to perform some optical simulations using the program Lumerical, i need a material's wavelength-dependent refractive index. The material is strongly absorbing in certain wavelengths (it is ...
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Which side is convex in my plano convex lens?

So, I am building an optical system and have got a Thorlabs plano-convex lens (part # LA1172-C) with a 400mm focal length. This makes the convex side of the lens so flat that it is difficult for me to ...
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1answer
43 views

Lens design with few constraints

I'm not an expert in lens design. I need to build a lens having fixed the focal point $f$, the lens diameter $D$, the maximum thickness $d$, the refractive index $n$ and the half-angle $\theta$ ...
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1answer
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Bubble optics, impact

My 8 years old daughter was blowing soap bubbles. Most of the bubbles had color. She randomly choses a bubble with colors and lands it on the wand. Instantly it's color is gone. If she blows this ...
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Raytracing on convex spherical surface, where n1>n2

I'm reading my textbook and I'm trying to figure the ray tracing of a single point of this one case that the book doesn't cover. My question is, what does the ray tracing look like when we have a ...
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1answer
44 views

Laser beam width distribution

I have questions about laser beam width. Beam divergence aside, does a laser beam has constant beam width? Are there any (micro)fluctuations in the width? Furthermore, is there a distribution for ...
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Calculating wavelength from diffraction grating equation [closed]

A diffraction grating with 750 slits per mm is illuminated by light which gives a first-order diffraction angle of 34.0 ∘. What is the wavelength of the light? So, I've got d as 750000, the angle as ...
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2answers
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How do lens capture reflections clearly?

In an optical system which uses lenses (cameras, our eye) multiple rays from the same point are conveyed in a single point on the retina / image sensor. This is typically shown as in the image below. ...
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Why the first ring's radius appears to be too little in newton's ring experiment?

In newton's ring experiment we should be going to see a large number of rings with their converging radius. But the ring right next to dark fringe is way nearer than 2nd or 3rd which appears to be an ...
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9 views

Spatial light modulator to generate LG beams

I am learning to use spatial light modulator. My problem is multiple rings coming out when I put the 1st mask (generating optical vortex) on SLM. It should be LG(0,-1) with only one ring. I did not ...
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Electron beam physics

I am looking for good resources to learn about electron beam optics to be able to characterize electron guns.
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Input Requirement for Gaussian to Flat-Top Conversion

I'm considering using a flat-top beam profile for laser micromachining instead of a Gaussian intensity profile. However, I don't want to lose the benefits of focusing a Gaussian profile rather than a ...
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Uncertainty of $\theta$ in Malus's law

Malus's law can be rearranged to this form $$\theta = \arccos\sqrt \frac{I}{I_0}.$$ $I_0$ is constant. $I$ has a variable uncertainty while $I_0$ has an uncertainty of 1. How can I find the ...
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1answer
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Collimating a UV LED

I have a task of narrowing a UV LED (375 to 400nm) of diameter 5mm to 1mm on the surface of an object. The LED has a peak output power of 2.2mw (quite low). It has an half Intensity angle of 10 ...
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How do I measure the (near) infra-red radiation intensity?

I need to measure how much of the radiation is absorbed by a specific fabric (as in "what percentage of photons is absorbed"). I am interested in 2 LEDs: 650nm (red) and 800nm (infra-red). The ...
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1answer
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Can an optical phased array be used to create free-floating holograms?

Frustratingly, most sources I've found about optical phased arrays only state that they can be used for "holograms" but do not explain what that means. Can optical phased arrays be used for "Star ...
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2answers
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Refractometers- Can the traditional prisms be substituted with some other component/s?

Is there any way we can substitute the prism that is used in refractometers? For example, introduce other components like lenses or sensors instead of a prism? An idea which could be tried? Could ...
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1answer
24 views

Telecentric lens system with gaussian optics

I often use bi-telecentric lenses at work, which means both object-side and image-side chief rays are parallel. However, as I don't really have an optics background, I'm a bit baffled at how this ...
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1answer
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“Partial” Total Internal Reflection

Can partial TIR happen? Consider the image present in this link Here, at point D, TIR happens, but also there is transmission. Is "total" internal reflection a misnomer?
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Integrating the dyadic Green function of a dipole source

I would like to ask if anyone know how to derive the equation (4) from this paper? I could not figure out how they derive the term $-\mathbf{P}_\mathrm{LO}(\mathbf{r})/3\varepsilon_0\varepsilon_B(\...
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1answer
77 views

Spatial wave-function of a single photon and its measurement

In the last decade there were several papers claiming that they've measured a "transverse quantum state" / "quantum wave-function" / "spatial Wigner function" of a single photon: Measurement of the ...
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2answers
25 views

How to find the radius of curvature of plano convex lens? [closed]

The information available about the lens are Refractive index n Aperture diameter d Maximum thickness of the lens t Is it possible to calculate the radius of curvature of the lens using the above ...
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1answer
29 views

Confusion regarding path difference by glass lab in YDSE

If in a YDSE experiment the setup is immersed in a medium $n_{med}$, and a glass slab of thickness t of another medium $n_{glass}$ is introduced in front of one slit, then is the path difference due ...
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1answer
30 views

Brillouin scattering in multimode fibers

Fiber ring resonators made up of single mode fibers often incorporate an optical isolator to suppress the build-up of Brillouin scattering. However, ring resonators made of multimode fibers generally ...
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1answer
324 views

How do car rear-view mirrors work? [closed]

I wonder, how does a car rear-view mirror work? When there is a car behind me with high-beam, all I do is flip a tong at the bottom of the mirror to relax the lights! Are there two mirrors in it, ...
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3answers
59 views

Polarisation of EM waves

My textbook reads 'The plane of polarisation of an electromagnetic wave is defined as the plane in which the electric field oscillates.' What exactly does this mean? I understand that an EM wave ...
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1answer
57 views

A method for a near/far sighted person to see clearly?

In all the diagrams showing a near/far sighted eye, the image is formed either in front or behind the retina. But what if the person tries not to focus at the object he is looking at? What I mean is ...
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26 views

Air wedge interferometer (Fringe separation)

From Hecht optics, From the setup, $ \alpha = \frac {d}{x}$ $--> d = x \alpha$ $d$ is the varying thickness of the air wedge The condition for constructive interference, $ ( m + \frac {1}{2} ) \...
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1answer
56 views

Faraday cages and what constitutes the minimum number of atoms to build an optical mirror

I recently asked this question: What is the minimum number of metal atoms necessary to make a mirror? However it seems I did not make myself clear enough about what I was looking for, even though the ...